The invention relates to an apparatus for the severing of a weft thread which is to be inserted into a shed and to a weaving machine with an apparatus of this kind.
In rapier weaving machines the weft thread travels from a supply bobbin via a plurality of operating units into the cloth and is held by the warp threads. For a respective subsequent weft insertion the relevant weft thread is presented to an inserting rapier and inserted by the latter into the shed, with the weft thread being severed at a time point which is determined by the machine control system. The known inserting rapiers have a thread clamp, the clamping force or clamping gap respectively of which is previously set. If the weft threads which are to be inserted have different thicknesses and/or if their surface nature is different, then the weft threads penetrate to different depths into the clamping gap of the thread clamp. This can have the result that the weft threads are not reliably clamped, i.e. held, or are even damaged. Since the weft threads are in each case severed at the same time within a weaving cycle in the known rapier weaving machines, it happens that a weft thread is, on the one hand, severed without a reliable holding in the clamping gap of the thread clamp and, on the other hand, a thin thread can be torn off even before it is severed by the severing apparatus. In the first case errors result in the insertion of the weft thread, so-called lost threads; in the other case the inserted weft thread can be too short and jump back into the cloth, which leads to weaving errors.